legacyshader.fxo/rez/shader

Hello,

ive a prob with pressing "F11" in game or in lobby got this for a month now tried some solutions but it didnt work heres what i tried:
1- re-installing the game
2- i suspected my graphs driver so ive re-installed it


heres the msg i get title "legacyshader.fxo/rez/shader" - msg in the mid of the msg.box "File not found" and then i get a black screen (in lobby only) and most of the weapons especially VIPs disappears. and once the game is over i canot join any other unless i restart the game.

also i get a send error report.

would have uploaded a SS if i know how..

both solutions didnt work.

help would be appreciated.

Thanks